In a remote copy operation, a line (for example, a line of a WAN (Wide Area Network) managed by a telecommunications vendor may be leased, and remote copying may be performed between storage systems by way of this leased line. For this reason, when the amount of data being sent and received between the storage systems increases, communications charges rise proportionally. These communications charges account for a large percentage of the costs involved in operating a remote copy system. Therefore, the smaller the amount of data sent and received between storage systems the better.
One method for reducing communications charges is to compress the data sent from the one storage system to the other storage system. However, the problem is that for a storage system, which does not comprise a data compression function, an appliance (a dedicated device) for compressing and sending data must be purchased and installed separately from the storage system, which is both costly and time consuming.
Another problem is that even though an appliance is purchased and installed, it is not possible to compress the data to be sent beyond expectations (that is, the data amount cannot be reduced very much). This is because the extent to which the data amount can be compressed depends on the type of data being sent, and until the appliance is actually operated, there is no way of identifying the type of data being handled. For example, in a case where the data to be sent is JPEG (Joint Photographic Experts Group) data, the JPEG data cannot be compressed much because it is already compressed.
Alternatively, there are storage systems, which use a storage device comprising a data compression function (for example, a SSD (Solid State Drive)). The SSD compresses write-target data, partitions the compressed data on the basis of the size of a page, which is the read/write unit, and writes the partitioned data to a page together with a guarantee code (for example, an ECC (Error Correcting Code)) for each write-destination page (Patent Literature 1).